Proposed Canon

"Decrypted" is the term given to the upgraded uncroaked (or "popped again") Wanda creates after attuning to the Arkenpliers. Decrypt is used as a verb (he was decrypted), an adjective (a decrypted unit), and a noun (decrypted retain their stats), similar to the usage of uncroaked. Decrypted superficially appear to be alive, lacking the physical evidence of the trauma that croaked them.

Decrypted are loyal to the tool wielder, regardless of past allegiances, but still remember their past loyalties, any information they knew in the past, and loves. Erf-b1.5-p033 They are also resistant to TurnamancyErf-b2-p29Erf-b2-p73, although the exact nature of their (in)ability to turn is unclear.

Decrypted units have zero upkeep cost and retain more of their pre-death strength, if not full strength, than uncroaked.Erf-b1-p145

When destroyed, Decrypted turn to dust like the Uncroaked. Units cannot be Decrypted more than once.Erf-b1.5-p043

Decrypted Natural Allies are units of the side of the wielder of the Arkenpliers, and don't count as a separate tribe, so if all members of a Natural Allies tribe are croaked, not even Decrypting them can allow to build more units of their former tribe.Erf-b1.5-p045

Speculation

The unit is enslaved to Wanda and may suffer a major mental attitude adjustment (e.g. "You were correct, of course. Royalty is obsolete."Erf-b1-p145) possibly due to a change in its Natural Thinkamancy or a choice made by Wanda at the time of decryption; otherwise, the Unit retains all of its previous stats, abilities, and levels, but it may suffer a demotion if it was of a high rank and that position is already occupied by another Unit.

As with uncroaking, uniforms and insignia are changed when the uncroaked join their new side. Decrypted seem to gain Wanda's insignia Erf-b1-p144 rather than the insignia of their chief warlord Erf-b1-p116, but this is Wanda's choice for units she creates Erf-b1.5-p026 rather than a feature of decryption itself. Units like Wiener-Rammers with no uniform may suffer a change of color in skin or fur.Erf-b1-p146

Wanda may be able to see through her units eyes, and if not, they will tell her anything relevant that happened to them. Erf-b1.5-p044

As they have zero upkeep, it is unlikely that any food pops for them, and thus unlikely that they need to eat and drink. It is unclear whether they can eat and drink.

It is unknown as of yet exactly how the Arkentools do what they do. It seems that they give Wanda an advanced form of Croakamancy, but it is a theory that it makes a combo-caster. Allowing Wanda to use a Croakamancy/Healomancy/Turnamancy spell to make the decrypted. Another possibility: could it be a form of Retconjuration, allowing Wanda to remake the croaked unit as she sees fit?

Being "popped again" is certainly a joking reference to the Christian concept of being born again, as being popped is the Erfworlders' version of being born, and Ansom, the one who coined the phrase, converted to Toolism upon being popped again and proceeded to evangelize his new faith.

Real World References

Decryption, in the real world, is used as the opposite of encryption, that is protecting data by turning it into a seemingly random sequence of symbols by means of a cypher and a key. Decryption is the opposite process, which takes useless gibberish and turns it into useful information, paralleling the process of taking a useless corpse and turning it into a useful creature. The same term is sometimes also used for removing desired content from protected sources (such as DVDs, music files and books). In this case, Wanda might have gained the ability to effectively remove the "DRM" from enemy units, allowing her to raise them without penalties and under her control. Alternately, the process of updating the MMORPG DDO contains a decrypting step, possibly suggesting the process is just an update to the units rules.

This makes the term a double pun, the 1st one being on "getting the unit out of a crypt".